JP6423352B2 - Holding pad - Google Patents

Description

  The present invention relates to a holding pad.

  Conventionally, when carrying out precision planar polishing of glass substrates such as semiconductor wafers, silicon wafers for semiconductor devices, substrates for various recording disks, and glass substrates for liquid crystal displays, the holding pad attached to the polishing head is used as an object to be polished. The object to be polished is held by being adsorbed with water and then polished using a polishing pad. The holding pad includes a sheet made of an elastic material such as polyurethane resin having open cells, and fine bubbles on the surface (holding surface) of the sheet can serve as a sucker to hold the object to be polished. . That is, the sheet functions as a holding layer.

  By the way, since the holding pad is exposed to a polishing liquid (polishing slurry) during the polishing process, the polishing liquid may infiltrate into open cells present in the holding layer of the holding pad. Once the polishing liquid enters, the elasticity of the elastic material constituting the holding layer is lost, or the holding layer swells, making it difficult to hold stably, and as a result, the polishing processability decreases. As a measure for preventing this, for example, Patent Document 1 discloses a holding pad containing a fluorine-based water repellent.

JP-A-9-254027

  When a water repellent as described in Patent Document 1 is used, it is possible to suppress the penetration of the polishing liquid into the holding layer. However, when the holding surface of the holding layer is moistened with water to adsorb the holding pad to the object to be polished, the familiarity with water decreases because of the presence of a water repellent agent, and the water repels Adsorption failure is likely to occur. On the other hand, if the amount of the water repellent added is reduced in order to prevent such adsorption failure, the dispersion of the water repellent will occur in the holding layer, resulting in the infiltration of water from weakly water repellent areas. During the processing, skin wear locally occurs in the holding layer, making it difficult to stably hold the object to be polished. Here, “skin abrasion” means that the holding layer swells due to water immersion or the like, so that the holding surface of the holding layer is scraped directly in contact with the polishing surface of the polishing pad, or the corner of the object to be polished This means that the holding surface that comes into contact is scraped off by the corners to open holes. These are because the holding layer swells and peels off from the polishing head and partially bends.

  This invention is made | formed in view of the said subject, and it aims at providing the holding pad which can suppress both the adsorption | suction defect of a to-be-polished object, and skin abrasion.

  As a result of intensive studies to achieve the above object, the present inventors have found that the holding pad has a moderately low storage elastic modulus E ′ at 40 ° C., and a water absorption amount by a specific water absorption measurement is in a proper range. It has been found that the above object can be achieved by providing the sheet as a holding layer, and the present invention has been completed.

That is, the present invention is as follows.
[1] A holding pad including a polyurethane resin sheet having a holding surface for holding an object to be polished, wherein the storage elastic modulus E ′ of the polyurethane resin sheet in a compression mode at 40 ° C. is 0.3 to 2.0 MPa. , and the and the water absorption of the polyurethane resin sheet 95~200mg / 50.3cm are ^two der, the water absorption, the polyurethane resin sheet was dried over 10 hours in a dryer of 40 ° C., room temperature 20 ° C. In the air atmosphere having a relative humidity of 50%, the polyurethane resin sheet after drying is naturally cooled to room temperature, and the first mass is measured. Then, on the polyurethane resin sheet, from the surface of the polyurethane resin sheet After holding the ion exchange water so that the height of the water surface becomes 60 mm and allowing it to stand for 8 hours, the ion exchange water is removed from the surface. The second mass is measured, a water absorption amount derived from the difference between the second mass and the first mass, the holding pad.
[2] The holding pad, wherein the polyurethane resin sheet has a KEL at 40 ° C. of 1.0 × 10 ^{5 to} 5.0 × 10 ⁵ Pa ⁻¹ .
[3] The holding pad as described above, wherein the resin constituting the polyurethane resin sheet has a 100% modulus at 25 ° C. of 4.0 to 10.0 MPa.
[4] The holding pad, wherein the polyurethane resin sheet contains a water repellent.
[5] The holding pad as described above, wherein the water repellent contains a fluorine-based water repellent having a perfluoroalkyl group having 6 to 8 carbon atoms.
[6] The holding pad, wherein 60 to 100 mol% of the fluorine-based water repellent contained in the polyurethane resin sheet is a fluorine-based water repellent having a C6 perfluoroalkyl group.

  ADVANTAGE OF THE INVENTION According to this invention, the holding pad which can suppress both the adsorption | suction failure of a to-be-polished object and skin abrasion can be provided.

It is sectional drawing which shows typically an example of the holding pad which concerns on this invention. It is a perspective view which shows typically the instrument used for the measurement of the adsorption amount concerning this invention.

  Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail with reference to the drawings as necessary. However, the present invention is limited to the following embodiment. It is not a thing. The present invention can be variously modified without departing from the gist thereof. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

The holding pad of this embodiment is a holding pad including a polyurethane resin sheet having a holding surface for holding an object to be polished, and the storage elastic modulus E ′ at 40 ° C. of the polyurethane resin sheet is 0.3-2. The water absorption of the polyurethane resin sheet is 95 to 200 mg / 50.3 cm ² .

  FIG. 1 is a schematic cross-sectional view showing an example of a holding pad according to the present embodiment. The holding pad 110 includes a polyurethane resin sheet (hereinafter simply referred to as “resin sheet”) 112 and a base material 114 laminated in this order. The resin sheet 112 and the base material 114 are joined to each other. In this example, the resin sheet 112 and the base material 114 are joined via the adhesive layer 116.

  The resin sheet 112 included in the holding pad 110 contains a polyurethane resin and functions as a holding layer having a holding surface P for holding an object to be polished. The storage elastic modulus E ′ of the resin sheet 112 is 0.3 to 2.0 MPa at 40 ° C. When the storage elastic modulus E ′ at 40 ° C. is 0.3 MPa or more, it is difficult for skin abrasion to occur on the resin sheet 112 during polishing. On the other hand, when the storage elastic modulus E ′ at 40 ° C. is 2.0 MPa or less, the adsorption force of the resin sheet 112 to the object to be polished is increased, and it is difficult to cause an adsorption failure. From the same viewpoint, the storage elastic modulus E ′ of the resin sheet 112 is preferably 0.4 to 1.5 MPa at 40 ° C., more preferably 0.5 to 1.0 MPa, and 0.5 to 0.00. More preferably, it is 7 MPa.

(Measurement method of storage elastic modulus E ′)
In the present specification, the storage elastic modulus E ′ of the resin sheet is 2 under the following conditions using a dynamic viscoelasticity measuring apparatus (for example, trade name “RSA III” manufactured by T.A. Instruments Japan). Sheets are measured and the arithmetic average is taken.
[Measurement condition]
・ Sample dimensions: 10 mm × 10 mm × Thickness 0.8 mm × 3 sheets stacked ・ Test direction: Compression mode ・ Load: 100 g / cm ²
-Strain: 0.10%
・ Frequency: 1 Hz
・ Temperature range: 20 to 80 ° C., heating rate: 5 ° C./min
-Sample thickness: Measured with a thickness meter-In the case of samples having different thicknesses, the thickness is measured in a range of 2 mm to 3 mm.

The water absorption of the resin sheet 112 is 95 to 200 mg / 50.3 cm ² . When the water absorption amount is 95 mg / 50.3 cm ² or more, the adsorption force of the resin sheet 112 to the object to be polished is increased, and it is difficult to cause poor adsorption. On the other hand, when the amount of adsorption is 200 mg / 50.3 cm ² or less, skin abrasion hardly occurs on the resin sheet 112 during polishing. From the same viewpoint, water absorption of the resin sheet 112 is preferable to be 100~160mg / 50.3cm ^2, more preferable to be 107~150mg / 50.3cm ^2, is 110~130mg / 50.3cm ² And more preferred.

(Measurement method of water absorption)
The water absorption amount of the resin sheet 112 is measured as follows. FIG. 2 is a perspective view schematically showing an instrument used for measuring the water absorption amount of the resin sheet. First, a holding pad 110 having a diameter φ of 125 mm, a butt-welded flange 20 made of vinyl chloride, and a plate flange 30 made of vinyl chloride (both JIS 10K-80A) are prepared. The flanges 20 and 30 have an inner diameter φ of 80 mm (a cross-sectional area of 50.3 cm ² ). Next, the sample 10 is dried in a dryer at 40 ° C. for 10 hours or more. Thereafter, the work is performed in an air atmosphere at a room temperature of 20 ° C. and a relative humidity of 50%. Next, the sample 10 is naturally cooled to room temperature in an air atmosphere, and its mass is measured with an electronic balance. Next, as shown in FIG. 2, the sample 10 is fixed by tightening from above and below with the holding surface P facing the butt weld flange 20 and sandwiching the sample 10 between the butt weld flange 20 and the plate flange 30. Next, 300 mL of ion-exchanged water W at 20 ° C. is injected into the pipe of the butt welding flange 20 (the height of the water surface from the holding surface P of the sample 10 at this time is about 60 mm). After the injection, they are allowed to stand for 8 hours, and then the sample 10 is released from the fixed state and taken out. At this time, moisture is absorbed by stroking the surface of the sample 10 without pressing the filter paper against the sample 10. Thereafter, the mass of the sample 10 is measured immediately. The difference in mass of the sample 10 before and after the ion-exchanged water W is injected and allowed to stand is defined as the water absorption amount of the resin sheet 112.

  As a method for controlling the resin sheet 112 according to the present embodiment to have the storage elastic modulus E ′ and the water absorption amount in the above-mentioned range, for example, 100% modulus at 25 ° C. of the resin constituting the resin sheet 112, 40 ° C. KEL, resin type, addition of water repellent, type and amount of the water repellent, thickness and density of the resin sheet 112, and buffing of the back side opposite to the skin layer of the resin sheet 112 A method of adjusting the amount is mentioned.

  The 100% modulus at 25 ° C. of the resin constituting the resin sheet 112 is preferably 4.0 to 10.0 MPa, more preferably 5.0 to 9.0 MPa, and 5.0 to 7.0 MPa. And more preferred. When the 100% modulus is 4.0 MPa or more, the storage elastic modulus E ′ of the resin sheet 112 tends to be 0.3 MPa or more, and when it is 10.0 MPa or less, the storage elastic modulus E of the resin sheet 112. 'Tends to be 2.0 MPa or less. In this specification, the 100% modulus is obtained when the non-foamed resin sheet (test piece) using the same material as the resin sheet 112 is stretched 100% in an environment of room temperature 23 ± 2 ° C., that is, the original length. It is a value obtained by dividing the tensile force when stretched twice the length by the initial cross-sectional area of the test piece.

KEL of the resin sheet 112 at 40 ° C. is preferably 1.0 × 10 ^{5 to} 5.0 × 10 ⁵ Pa ⁻¹ and is 1.5 × 10 ^{5 to} 4.0 × 10 ⁵ Pa ^−1. more preferably, further preferable to be ^{2.0 × 10 5 ~3.0 × 10 5} Pa -1. When this KEL is 1.0 × 10 ⁵ Pa ⁻¹ or more, the resin sheet 112 is easily deformed, and it is possible to improve the retention and adsorption of the object to be polished. Further, it becomes difficult for the object to be polished to shift in the in-plane direction during polishing. On the other hand, when KEL is 5.0 × 10 ⁵ Pa ⁻¹ or less, the amount of deformation of the resin sheet 112 is reduced (that is, the amount of sinking of the resin sheet 112 during polishing) is reduced, and the skin wear is reduced. Can be further suppressed, and the life of the holding pad 110 can be extended.

(Calculation method of KEL)
In the present specification, KEL (energy loss factor) is calculated from the following equation based on the storage elastic modulus E ′ and loss elastic modulus E ″ measured at 40 ° C. under the same conditions as those of the “method for measuring storage elastic modulus E ′”. Calculated by (1a) and (1b).
KEL = tan δ × 10 ¹² / (E ′ × (1 + tan δ ² )) (1a)
tan δ = E ″ / E ′ (1b)

The density (bulk density) of the resin sheet 112 according to the present embodiment is preferably 0.15 to 0.30 g / cm ² at 25 ° C. When this density is 0.15 g / cm ² or more, permanent deformation of the resin sheet 112 becomes difficult to occur, and when it is 0.30 g / cm ² or less, the entire resin sheet 112 is polished. It becomes easier to hold objects more uniformly. As a result, when the density of the resin sheet 112 is in the above range, the object to be polished is displaced in the in-plane direction with respect to the holding pad 110 during polishing processing, or uneven polishing occurs during polishing processing. Further suppression can be achieved.

Although the thickness of the resin sheet 112 is not specifically limited, For example, 0.2-1.5 mm may be sufficient and 0.6-1.2 mm may be sufficient. In addition, the thickness of the resin sheet 112 is measured based on the measuring method described in JIS K 6550 (1994). That is, it is the thickness when a load of 100 g per 1 cm ² is applied (loaded) as the initial load in the thickness direction of the resin sheet 112.

  The resin sheet 112 has a plurality of bubbles (not shown) in a material constituting a matrix such as a resin (hereinafter referred to as “matrix material”), and is formed by a so-called wet film forming method. However, from the viewpoint of more effectively and reliably achieving the object of the present invention, it is preferably formed by a wet film forming method. When the resin sheet 112 is formed by a wet film forming method, it may have a skin layer in which fine micropores (not shown) are formed on the holding surface P side. The surface of the skin layer has fine flatness. On the other hand, on the inner side of the skin layer (inside the resin sheet 112), the pores having a larger diameter than the fine pores of the skin layer and having a round cross section along the thickness direction of the resin sheet 112 (open cells) ; Not shown) may be formed. The holes may be formed such that the size on the holding surface P side is smaller than the surface side opposite to the holding surface P. The resin sheet 112 may be formed with holes (not shown) having a size larger than the fine pores of the skin layer and smaller than the pores. The fine pores, pores, and small-sized pores of the skin layer may be connected to each other in a mesh shape through communication holes.

  The matrix material constituting the resin sheet 112 is not particularly limited as long as it is a composition containing the most polyurethane resin. For example, the resin sheet 112 may include 80 to 100% by mass of polyurethane resin with respect to the total amount of the matrix material. It may be included. The resin sheet 112 more preferably contains 85 to 100% by mass of polyurethane resin, more preferably 90 to 100% by mass, and particularly preferably 90 to 95% by mass with respect to the total amount.

  Examples of the polyurethane resin include a polyester-based polyurethane resin, a polyether-based polyurethane resin, and a polycarbonate-based polyurethane resin, and these are used singly or in combination of two or more. Among these, polyester polyurethane resins are preferred from the viewpoint of more effectively and reliably achieving the object of the present invention.

  The polyurethane resin may be synthesized by a conventional method, or a commercially available product may be obtained. Examples of commercially available products include Crisbon (trade name, manufactured by DIC Corporation), Samprene (trade name, manufactured by Sanyo Chemical Industries, Ltd.), Rezamin (trade name, manufactured by Dainippon Seika Kogyo Co., Ltd.). It is done. A polyurethane resin is used individually by 1 type or in combination of 2 or more types.

  The resin sheet 112 may include other resins such as a polysulfone resin and / or a polyimide resin in addition to the polyurethane resin. The polysulfone resin may be synthesized by a conventional method, or a commercially available product may be obtained. Examples of commercially available products include Udel (trade name manufactured by Solvay Advanced Polymers Co., Ltd.). The polyimide resin may be synthesized by a conventional method, or a commercially available product may be obtained. Examples of commercially available products include Aurum (trade name, manufactured by Mitsui Chemicals, Inc.).

  The resin sheet 112 preferably contains a water repellent in addition to the matrix material. Examples of the water repellent include a fluorine water repellent, a silicon water repellent, and a hydrocarbon water repellent. Among these, a fluorine-based water repellent is preferable from the viewpoint of more effectively and reliably achieving the object of the present invention. A water repellent is used individually by 1 type or in combination of 2 or more types.

As a fluorine-type water repellent, the compound (fluorine-type water repellent) which has a perfluoroalkyl group is mentioned, for example, Preferably, the fluorine telomer represented by following formula (2) is mentioned.
Rf-R-X (2)
Here, Rf represents a perfluoroalkyl group, and the carbon number thereof is 3 to 8, preferably 4 to 8, more preferably 6 to 8, and particularly preferably 6. R represents an alkylene group having 2 to 6 carbon atoms, preferably 2 to 4 carbon atoms, and particularly preferably 2 carbon atoms. X represents a functional group, for example, a hydroxyl group, CH ₂ ═CHC (═O) CO—, H (OCH ₂ CH ₂ ) _x O—, YSO ₃ — [Y represents a hydrogen atom or NH ₄ . And the like, preferably a hydroxyl group. Moreover, the compound which modified | denatured resin with the perfluoroalkyl group as a compound which has a perfluoroalkyl group is also mentioned. Examples of the resin include a resin that can form the resin sheet of the holding pad, for example, a polyurethane resin, from the viewpoint of improving dispersibility and aging stability with respect to the resin sheet. The method of introduce | transducing a perfluoroalkyl group into a side chain is mentioned. The compound which has a perfluoroalkyl group is used individually by 1 type or in combination of 2 or more types.

  Among the fluorine telomers, from the viewpoint of more effectively and reliably achieving the object of the present invention, those having 6 carbon atoms in Rf are preferable, and those having 2 carbon atoms in R are more preferable. In consideration of dispersibility and aging stability with respect to the resin sheet, a compound in which the resin is modified with a perfluoroalkyl group, a compound in which a fluorine telomer is introduced into the resin, for example, Rf-R in the above formula (2) A resin having a group represented by-is preferred, and a polyurethane resin having a group represented by Rf-R- in the above formula (2) is more preferred. Examples of such a resin include polyurethane resins described in International Publication No. 2012/172936.

  The fluorine telomer may be synthesized by a conventional method, or a commercially available product may be obtained. Commercially available products include, for example, Chris Bon Asister SD Series (trade name, manufactured by DIC Corporation), Asahi Guard E Series (trade name, manufactured by AGC Seimi Chemical Co., Ltd.), NK Guard S Series (trade name, manufactured by Nikka Chemical Co., Ltd.) And Unidyne Multi series (trade name, manufactured by Daikin Industries, Ltd.). A fluorine telomer is used individually by 1 type or in combination of 2 or more types.

The content of the water repellent in the resin sheet 112 is preferably 2 to 14 parts by mass and more preferably 3 to 13 parts by mass with respect to 30 parts by mass of the resin constituting the resin sheet 112. When the content of the water repellent is 2 parts by mass or more with respect to 30 parts by mass of the resin, the water absorption is likely to be 200 mg / 50.3 cm ² or less, and the localization of the water repellent is prevented. Therefore, local skin abrasion can be suppressed. Moreover, when the content of the water repellent is 14 parts by mass or less with respect to 30 parts by mass of the resin, the water absorption easily becomes 95 mg / 50.3 cm ² or more. Further, in the manufacturing method of the holding pad 110 described later, when the resin sheet 112 is produced through the coagulation regeneration process, and the water repellent is included in the resin solution before the coagulation regeneration process, the solidification unevenness is produced. As a result, film formation unevenness of the resin sheet 112 can be further suppressed.

  Further, when a fluorine-based water repellent such as a fluorine telomer is used as the water repellent and the fluorine-based water repellent includes a fluorine-based water repellent having Rf of 6 carbon atoms, the fluorine-based resin contained in the resin sheet 112 It is preferable that 60 to 100 mol% of the water repellent is a fluorine-based water repellent having Rf having 6 carbon atoms. This limits compounds containing a large amount of fluorine atoms such as fluorine telomers having an Rf with more than 6 carbon atoms and compounds containing few fluorine atoms such as fluorine telomers having an Rf having less than 6 carbon atoms. become. As a result, the content of the compound containing a large amount of fluorine atoms can be reduced to more effectively suppress the decrease in water absorption and poor adsorption, and the content of the compound containing a small amount of fluorine atoms can be reduced to an appropriate level. Water repellency can be more effectively ensured.

  The resin sheet 112 is a material normally used for the resin sheet of the holding pad, for example, a pigment such as carbon black, a hydrophilic additive, and the like, as long as the solution of the problem of the present invention is not hindered in addition to the resin and an optional water repellent. One or more hydrophobic additives may be included. Furthermore, various materials such as a solvent used in the manufacturing process of the resin sheet 112 may remain in the resin sheet 112 within a range that does not hinder the solution of the problems of the present invention.

  Fine pores may exist on the holding surface P of the resin sheet 112. The fine pores can be formed, for example, by adding an additive that forms fine pores on the holding surface (skin layer) when the resin sheet 112 is formed.

  The base material 114 provided in the holding pad 110 is for supporting the resin sheet 112 and is not particularly limited, and may be included as a base material in a conventional holding pad. Specifically, Examples thereof include resin films such as polyethylene terephthalate (hereinafter referred to as “PET”) films.

  Further, the adhesive layer 116 may include an adhesive or a pressure-sensitive adhesive used for a conventionally known holding pad. Examples of the material of the adhesive layer 116 include various thermoplastic adhesives such as acrylic, nitrile, nitrile rubber, polyamide, polyurethane, and polyester.

  The base material 114 and the adhesive layer 116 in the holding pad 110 may be derived from a double-sided tape including them. The double-sided tape has an adhesive layer containing an adhesive or a pressure-sensitive adhesive on both surfaces of the substrate 114, and one adhesive layer corresponds to the adhesive layer 116. The other adhesive layer is for attaching the holding pad 110 to the holding surface plate of the polishing machine. The double-sided tape may be included in a conventional holding pad, and may have a release paper (not shown) on the side opposite to the substrate 114.

  Next, an example of the manufacturing method of the holding pad of this embodiment will be described. Here, the case where the resin sheet 112 is manufactured by a wet film formation method will be described; however, the method for manufacturing the resin sheet 112 is not limited to this. This manufacturing method includes a step of preparing the resin sheet 112 and a step of obtaining the holding pad 110 by bonding the base material 114 to the resin sheet 112.

  The step of preparing the resin sheet 112 further includes a step of preparing a resin solution containing a resin, a solvent, and, if necessary, a water repellent (resin solution preparation step), and the resin solution on the surface of the substrate for film formation. A step of applying (coating step), a step of coagulating and regenerating the resin in the resin solution to form a precursor sheet (coagulation regenerating step), and a step of removing the solvent from the precursor sheet to obtain the resin sheet 112 ( Solvent removal step) and a step of grinding and / or partially removing the resin sheet 112 by buffing or slicing (grinding / removing step). Hereinafter, each step will be described.

  First, in the resin solution preparation step, a resin such as the above-mentioned polyurethane resin, a solvent that can dissolve the resin, and a water-repellent agent that is included in the resin sheet 112 as necessary, and a solvent that is miscible with the coagulation liquid described below, and Other materials (for example, a pigment, a hydrophilic additive, and a hydrophobic additive) are mixed, and if necessary, defoamed under reduced pressure to prepare a resin solution. The solvent is not particularly limited, and examples thereof include N, N-dimethylformamide (hereinafter referred to as “DMF”) and N, N-dimethylacetamide. Although content of resin with respect to the whole quantity of a resin solution is not specifically limited, For example, the range of 10-50 mass% may be sufficient, and the range of 15-35 mass% may be sufficient.

  Next, in the coating step, the resin solution is preferably applied to the surface of the belt-shaped film-forming substrate using a coating device such as a knife coater at room temperature to form a coating film. What is necessary is just to adjust suitably the thickness of the resin solution apply | coated at this time so that the thickness of the resin sheet 112 finally obtained may become desired thickness. Examples of the material for the film forming substrate include a resin film such as a PET film, a fabric, and a nonwoven fabric. In these, resin films, such as a PET film which cannot permeate | transmit a liquid, are preferable.

  Next, in the coagulation regeneration step, the coating film of the resin solution applied to the film-forming substrate is continuously guided into a coagulating liquid mainly composed of a poor solvent for the resin (for example, water in the case of a polyurethane resin). . In order to adjust the regeneration speed of the resin, an organic solvent such as a polar solvent other than the solvent in the resin solution may be added to the coagulation liquid. The temperature of the coagulation liquid is not particularly limited as long as the resin can be coagulated, and may be, for example, 15 to 65 ° C. In the coagulation liquid, first, a film (skin layer) is formed at the interface between the coating film of the resin solution and the coagulation liquid, and innumerable fine micropores are formed in the resin immediately adjacent to the film. Thereafter, regeneration of the resin preferably having an open-cell structure proceeds by the cooperative phenomenon of diffusion of the solvent contained in the resin solution into the coagulation liquid and penetration of the poor solvent into the resin. At this time, if the film-forming substrate is difficult to penetrate the liquid (for example, PET film), the coagulating liquid does not penetrate the substrate, so the substitution of the solvent in the resin solution with the poor solvent is near the skin layer. The voids are preferentially generated in the region, and larger pores tend to be formed in the region inside the skin layer than in the vicinity thereof. Thus, a precursor sheet is formed on the film forming substrate.

  When the resin solution contains a water repellent, if the content of the water repellent is 14 parts by mass or less with respect to 30 parts by mass of the resin, solidification unevenness that may occur due to interference between the water repellent and the coagulation liquid is further reduced. Since it can suppress, it becomes possible to prevent the film formation nonuniformity of the resin sheet 112 obtained as a result more.

  Next, in the solvent removal step, the solvent remaining in the formed precursor sheet is removed to obtain the resin sheet 112. For removing the solvent, a conventionally known cleaning solution can be used. Moreover, you may dry the resin sheet 112 after removing a solvent as needed. For example, a cylinder dryer provided with a cylinder having a heat source can be used for drying the resin sheet 112, but the drying method is not limited to this. When a cylinder dryer is used, the precursor sheet is dried by passing along the peripheral surface of the cylinder. Furthermore, the obtained resin sheet 112 may be wound into a roll.

  Next, in the grinding / removal step, preferably, at least one of the main surface on the skin layer side and the back surface on the opposite side of the resin sheet 112 is ground and / or partially removed by buffing or slicing. . Since the thickness of the resin sheet 112 can be made uniform by buffing or slicing, the pressing force on the object to be polished is further equalized, and the damage to the object to be polished is further suppressed and the flatness of the object to be polished is improved. Can be improved. Moreover, since the main surface on the skin layer side is a surface that becomes the holding surface P in the resin sheet 112, it is preferable to grind the back surface to improve the polishing uniformity of the object to be polished.

  Next, the base material 114 is bonded to the resin sheet 112 to obtain the holding pad 110. In this step, for example, the base material 114 is bonded to the surface of the resin sheet 112 opposite to the holding surface P through the adhesive layer 116 using a double-sided tape having the base material 114 and the adhesive layer 116. Further, the other adhesive layer of the double-sided tape and the release paper may be provided on the opposite side of the base material 114 from the adhesive layer 116. In this way, the holding pad 110 is obtained.

  Next, a polishing method using the holding pad 110 of this embodiment will be described. The object to be polished in the polishing process is not particularly limited, and examples thereof include materials for semiconductors, silicon wafers for semiconductor devices, substrates for various recording disks, and glass substrates for liquid crystal displays. Of these, the object to be polished is preferably a glass substrate from the viewpoint of more effectively and reliably achieving the effects of the present invention.

  In the polishing process, first, the holding pad 110 is mounted on the object holder of the polishing machine, and the object to be polished is held by the holding pad 110. In order to attach the holding pad 110 to the workpiece holder, the release paper of the double-sided tape is removed as necessary, and the holding surface P is adhered to the workpiece holder so that the holding surface P faces downward (or upward) with the exposed adhesive layer. Fix it. Alternatively, when the holding pad 110 is not provided with a double-sided tape, the holding pad 110 is bonded and fixed to the workpiece holder with a separately prepared adhesive or adhesive. Next, an appropriate amount of water is included in the holding surface P of the resin sheet 112 and the object to be polished is pressed, so that the object to be polished is polished through the holding pad 110 due to the surface tension of the water and the adhesiveness of the resin sheet 112. It is held by the object holder. At this time, the surface to be polished (processed surface) of the object to be polished faces downward (or upward). On the other hand, a polishing surface plate placed on the surface of the polishing platen so as to face the polishing object holder below (or above) the polishing object holder has a polishing pad (polishing cloth) on the surface and a polishing surface above (or below). Wear it so that it faces.

Next, the object to be polished is transported by moving the object holder to the polishing surface plate so that the object surface to be polished contacts the polishing surface of the polishing pad. Then, a polishing slurry containing chemical components such as abrasive grains (polishing particles; for example, SiO ₂ , CeO ₂ ) and an oxidant represented by hydrogen peroxide is circulated and supplied between the object to be polished and the polishing pad. At the same time, the processed surface of the object to be polished is polished by CMP with the polishing pad by rotating the object holder and the polishing surface plate while pressing the object to be polished toward the polishing pad with the object holder. Is done.

In the present embodiment, the storage elastic modulus E ′ at 40 ° C. of the resin sheet 112 is 0.3 to 2.0 MPa, and the water absorption amount of the resin sheet 112 is 95 to 200 mg / 50.3 cm ² . It is possible to suppress both the adsorption failure of the workpiece and the skin abrasion. When the storage elastic modulus E ′ at 40 ° C. is 0.3 MPa or more, it is difficult for skin abrasion to occur on the resin sheet 112 during polishing. On the other hand, when the storage elastic modulus E ′ at 40 ° C. is 2.0 MPa or less, the adsorption force of the resin sheet 112 to the object to be polished is increased, and it is difficult to cause an adsorption failure. Furthermore, when the water absorption amount is 95 mg / 50.3 cm ² or more, the adsorption force of the resin sheet 112 to the object to be polished is increased, and it is difficult to cause poor adsorption. On the other hand, when the amount of adsorption is 200 mg / 50.3 cm ² or less, skin abrasion hardly occurs on the resin sheet 112 during polishing. Suppressing the occurrence of skin abrasion prevents the holding surface P from being damaged. As a result, the life of the holding pad 110 is extended.

  Although the present embodiment has been described in detail above, the present invention is not limited to the present embodiment. For example, in the present embodiment, the adhesive layer 116 is used for joining the resin sheet 112 and the base material 114, but the joining is not limited to using the adhesive layer 116. Furthermore, the holding pad of the present invention may not include a substrate, but it is preferable to include a substrate from the viewpoint of the handleability of the holding pad. Further, in the manufacturing method of the holding pad, the grinding / removal step may be omitted. Further, in the manufacturing method of the holding pad, instead of or in addition to adding a water repellent to the resin solution, after applying the water repellent to the obtained resin sheet, it is dried as necessary. The resin sheet may contain a water repellent. Examples of the method for applying the water repellent include a dipping method and a spray method.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

Example 1
For 100 parts by mass of a 30% DMF solution of a polyester polyurethane resin having a 100% modulus (at 25 ° C., the same applies hereinafter), which is a raw material resin, of 6.0 MPa, 50 parts by mass of DMF, 8 parts by mass of water, As a liquid agent, 3 parts by mass of “Crisbon Assister SD-38” (trade name) manufactured by DIC Corporation containing a perfluorohexyl compound was added, mixed and stirred to prepare a resin solution. Next, a PET film was prepared as a substrate for film formation, and the resin solution was applied thereto using a knife coater to obtain a coating film having a thickness of 1.0 mm. Polyester polyurethane resins include polyester polyols obtained by dehydration condensation of ethylene glycol and propylene glycol and adipic acid, methylenebis (4,1-phenylene) = diisocyanate (MDI), and low molecular diols. (The same applies to the following Examples and Comparative Examples).

  Next, the obtained coating film was immersed in an 18 ° C. coagulation bath made of water as a coagulation liquid together with the film forming substrate, and the resin was coagulated and regenerated to obtain a precursor sheet. After removing the precursor sheet from the coagulation bath and peeling the substrate for film formation from the precursor sheet, the precursor sheet is immersed in a room temperature cleaning solution (desolvent bath) made of water to remove DMF as a solvent. A resin sheet was obtained. Thereafter, the resin sheet was wound up while being dried. Next, the back surface of the resin sheet (the surface on the side where the film-forming substrate was peeled off and the surface that was in contact with the film-forming substrate) was buffed to a thickness of 0.8 mm. .

  Next, a double-sided tape having an adhesive layer (material: acrylic resin) on both sides of a PET substrate and a release paper on one side is provided on the surface of the resin sheet subjected to the buff treatment, and the release paper After bonding with the adhesive layer on the opposite side, it was cut into a circle with an outer diameter of 33.5 cm to obtain a holding pad.

  The storage elastic modulus E ′ at 40 ° C. of the resin sheet provided in the holding pad is the “method for measuring storage elastic modulus E ′”, the water absorption is the “method for measuring water absorption”, and the KEL at 40 ° C. is the above “KEL Each was measured by “calculation method”. In the method for measuring the storage elastic modulus E ′ and KEL, a product name “RSA III” manufactured by TA Instruments Japan Co., Ltd. was used as a dynamic viscoelasticity measuring apparatus.

(Measurement of adsorption power)
The holding pad was cut into a square of about 100 mm × 100 mm. A glass substrate having a diameter of 60 mm and a thickness of about 1 mm was prepared as an object to be adsorbed. The cut out holding pad was mounted on a fixed surface plate. Next, an appropriate amount of water was sprayed onto the holding surface of the resin sheet provided in the holding pad, and after appropriate drainage, the glass substrate was firmly pressed against the holding pad to be adsorbed. Next, the jig | tool for tension | pulling was firmly pressed and affixed on the surface on the opposite side to the holding pad side of a glass substrate through the double-sided tape with a cushion layer of the same size as a glass substrate. Thereafter, the tensile jig was pulled to the opposite side of the glass substrate, and the maximum value of the tensile load when the glass substrate was pulled away from the holding pad was read. TENSILON (manufactured by ORIENTEC) was used as a tensile tester. The above operation is repeated three times without changing the holding pad mounted on the workpiece holder (however, after the second time, the glass substrate is held with the tension jig attached to the glass substrate. The maximum value of the three tensile loads was arithmetically averaged to obtain the adsorption force.

(Holding pad life measurement)
A holding pad was attached to a predetermined position of a polishing machine (trade name “SP-1200” manufactured by Speed Fem Co., Ltd.). Next, after spraying an appropriate amount of water onto the holding surface of the resin sheet provided in the holding pad and draining it appropriately, the glass substrate for liquid crystal display (470 mm × 370 mm × 0.5 mm) as the object to be polished is adsorbed to the holding pad. I let you. Polishing was performed under the following conditions using Polypass FX-7M (trade name, manufactured by Fujibow Atago Co., Ltd.) as a polishing pad. Polishing is performed until polishing is no longer possible when the object to be polished is detached from the holding pad and damaged, or when the skin wear occurs on the holding pad, and the holding pad is determined depending on the number of objects to be polished. Lifespan was evaluated. The maximum number of objects to be polished was 50.
Used polishing machine: Oscar polishing machine SP-1200 (trade name made by Speed Fem Co., Ltd.)
Polishing speed (rotation speed): 61 rpm
Processing pressure: 76 gf / cm ²
Slurry: Show Rocks A-10 (trade name, manufactured by Showa Denko KK) 10% slurry Polishing time: 10 minutes / sheet Table 1 shows the results of the above measurements.

(Example 2)
A holding pad was prepared in the same manner as in Example 1 except that the amount of the water repellent added was changed to 7 parts by mass with respect to 100 parts by mass of the 30% DMF solution of the polyester polyurethane resin, and each measurement was performed. The results of each measurement are shown in Table 1.

(Example 3)
A holding pad was prepared in the same manner as in Example 1 except that the amount of the water repellent added was changed to 10 parts by mass with respect to 100 parts by mass of the 30% DMF solution of the polyester polyurethane resin, and each measurement was performed. The results of each measurement are shown in Table 1.

Example 4
A holding pad was prepared in the same manner as in Example 1 except that the amount of the water repellent added was changed to 13 parts by mass with respect to 100 parts by mass of the 30% DMF solution of the polyester polyurethane resin, and each measurement was performed. The results of each measurement are shown in Table 1.

(Example 5)
A holding pad was prepared in the same manner as in Example 3 except that the raw material resin was changed to a polyester polyurethane resin having a 100% modulus of 8.4 MPa, and each measurement was performed. The results of each measurement are shown in Table 1.

(Comparative Example 1)
A holding pad was produced in the same manner as in Example 3 except that the raw material resin was changed to a polyester polyurethane resin having a 100% modulus of 3.0 MPa, and each measurement was performed. The results of each measurement are shown in Table 1.

(Comparative Example 2)
A holding pad was prepared in the same manner as in Example 3 except that the water repellent was changed to “Crisbon Assister SD-27” (trade name) manufactured by DIC Corporation containing a perfluorooctyl compound, and each measurement was performed. It was. The results of each measurement are shown in Table 1.

(Comparative Example 3)
A holding pad was produced in the same manner as in Example 1 except that the amount of the water repellent added was changed to 1 part by mass with respect to 100 parts by mass of the 30% DMF solution of the polyester polyurethane resin, and each measurement was performed. The results of each measurement are shown in Table 1.

(Comparative Example 4)
A holding pad was prepared in the same manner as in Example 1 except that the amount of the water repellent added was changed to 15 parts by mass with respect to 100 parts by mass of the 30% DMF solution of the polyester polyurethane resin, and each measurement was performed. The results of each measurement are shown in Table 1.

(Comparative Example 5)
A holding pad was produced in the same manner as in Example 3 except that the raw material resin was changed to a polyester polyurethane resin having a 100% modulus of 20 MPa, and each measurement was performed. The results of each measurement are shown in Table 1.

  In the measurement of the life of the holding pad, in Comparative Examples 1 and 3, skin abrasion occurred on the resin sheet, and as a result of the object to be polished being displaced in the in-plane direction of the holding pad, polishing became difficult. Further, in Comparative Examples 2, 4, and 5, polishing was difficult as a result of the object to be polished peeled off from the holding pad.

  The holding pad of the present invention is suitably used for polishing processing using a semiconductor, a silicon wafer for semiconductor devices, a substrate for various recording disks, a glass substrate for liquid crystal display, etc. as an object to be polished. There is a possibility of use.

  DESCRIPTION OF SYMBOLS 110 ... Holding pad 112 ... Polyurethane resin sheet, 114 ... Base material, 116 ... Adhesive layer, P ... Holding surface

Claims (6)

A holding pad including a polyurethane resin sheet having a holding surface for holding an object to be polished, wherein the polyurethane resin sheet has a storage elastic modulus E ′ in a compression mode at 40 ° C. of 0.3 to 2.0 MPa, and water absorption of the polyurethane resin sheet Ri 95~200mg / 50.3cm ² der,
The water absorption is such that the polyurethane resin sheet is dried in a dryer at 40 ° C. for 10 hours or longer, and the dried polyurethane resin sheet is naturally cooled to room temperature in an air atmosphere at a room temperature of 20 ° C. and a relative humidity of 50%. The first mass was measured, and then the ion-exchanged water was held on the polyurethane resin sheet so that the water surface had a height of 60 mm from the surface of the polyurethane resin sheet, and allowed to stand for 8 hours. A holding pad which is a water absorption amount derived from a difference between the first mass and the second mass by removing the ion exchange water from the surface and measuring a second mass . The KEL at 40 ° C. of the polyurethane resin sheet is ^{1.0 × 10 5 ~5.0 × 10 5} Pa -1, holding pad of claim 1.   The holding pad according to claim 1 or 2, wherein the resin constituting the polyurethane resin sheet has a 100% modulus at 25 ° C of 4.0 to 10.0 MPa.   The holding pad according to any one of claims 1 to 3, wherein the polyurethane resin sheet contains a water repellent.   The holding pad according to claim 4, wherein the water repellent includes a fluorine-based water repellent having a perfluoroalkyl group having 6 to 8 carbon atoms.   The holding pad according to claim 5, wherein 60 to 100 mol% of the fluorine-based water repellent contained in the polyurethane resin sheet is a fluorine-based water repellent having a C6 perfluoroalkyl group.

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